The invention relates to a cooling air blower for a combustion engine, especially for two-stroke engines for hand-held tools such as motor-driven chain saws, blowing devices, cutting-off machines etc., which have a blower fan that supplies cooling air for the combustion engine to a cooling air channel. The cooling air blower further has a combustion air channel branching off the cooling air channel which supplies the intake member of the combustion engine with combustion air needed for operation, whereby the combustion air channel has one section that is adjacent to the cooling air channel and is provided with an inlet opening for allowing air from the cooling air channel into the combustion air channel.
In a known cooling air blower according to Swedish printed document 442 232 the combustion air channel is positioned approximately in a plane parallel to the radial blower fan and limits axially a cooling air spiral surrounding the blower fan. An annular slot is provided within the combustion air channel and is facing the cooling air channel, whereby the annular slot is covered relative to the blower fan by a baffle plate in order to prevent a direct introduction of dirt particles contained within the cooling air into the combustion air channel. Due to the great extension of the annular slot a considerable disturbance of the cooling air flow within the cooling air spiral occurs which may result in an impairment of the cooling effect of the combustion engine. Furthermore, the annular slot is positioned close to the exit of the cooling air spiral where a relatively high static pressure is present which favors the transfer of dirt particles from the cooling air flow into the combustion air channel.
It is therefore an object of the present invention to improve a cooling air blower of the aforementioned kind such that with a relatively low disturbance of the cooling air flow even great amounts of substantially dirt particle-free combustion air can be branched off.